Availability analysis of a certain class of distributed computer systems under the influence of hardware and software faults

There are modeling techniques which may be used to assess the availability of either the software or the hardware of distributed computer systems. However, from the practical point of view, it would be more useful to assess the availability when the system is subjected to the combined effect of hardware and software faults either during its normal operating time or repair time. Such an availability modelling technique, for the class of distributed computer systems which are used for process control is presented in this paper. To demonstrate the use of this technique the time function of the availability of a typical real-life distributed process control system is evaluated.